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Your aquarium filtration capacity for above selected species is 79%.
Recommended water change schedule: 62% per week. (You might want to split this water change schedule to two separate 38% per week)
Your aquarium stocking level is 176%.
Your tank is overstocked. Unless you are an experienced aquarist who can meet the maintenance/biological needs of this aquarium, lower stocking levels are recommended

I've been at this capacity since June 2010. Should I be worried? I only do 20% once per week. Am I defying science? haha... or are my fish suffering?

you are extremely overstocked and defying science. all the filtration in the world won't help you with uch cramped space. I'm surprised there isn't a ton of aggression, although some will overstock to avoid any one fish getting picked on. something bad could happen anytime with those fish. especially when becomming adults and spawning occurs.

Those nitrAtes are quite high. Is that the level when you do your water change? Either way I strongly recommend you increase your water changes to 40-50%.

My nitrate level is around 60-80ppm before I do my water change. 3 hours after my water change, the nitrate level is around 30-40 ppm

Originally Posted by Crispy

you are extremely overstocked and defying science. all the filtration in the world won't help you with uch cramped space. I'm surprised there isn't a ton of aggression, although some will overstock to avoid any one fish getting picked on. something bad could happen anytime with those fish. especially when becomming adults and spawning occurs.

Surprisingly enough, there isn't much aggression in the tank. They all just swim with each other and look happy. I have a video of their behavior:

Also, green algae always builds up on the walls of my tank. I have to get a dish towel and wipe the algae off once per month to clean the glass. Is there anything I can do to stop green algae build up? It's not abnormal algae, just the normal green algae that you would find in any other tank. It just builds up very quickly.

You are soon to find the downside of Mbuna I wager. Wait until they hit fishy puberty and start spawning. Total game changer. That many fish in a 55g is WAY too many to begin with, not to mention hyper-aggressive. Keep in mind every one of these can get 4-6" each.

Hope you have a lot of rock work. And I agree, up the water changes.

Just watched your video..those are BABIES but getting closer to becoming terrors. Just wait. It always happens when you least expect it. Then BAM, dead fish.

80ppm is way above ideal. Generally you want to keep them below 40ppm. That is my water change point, not what I shoot for during water changes.

And I gotta know, what magical method do you use to go from 80ppm to 40ppm by changing 20% of the water? if you did a 50% change, that would make sense. Otherwise I think one of your measurements is off.

My nitrate level is around 60-80ppm before I do my water change. 3 hours after my water change, the nitrate level is around 30-40 ppm

In that case I would absolutely up water changes. You're letting your nitrates get to harmful levels, especially in the days leading up to your water change.

I can't comment on your stock level because I'm not familiar with african cichlids. However I know that Crispy runs a tank that a lot of people have called overstocked (he makes it work with good maintenance and massive filtration) - so if he says you're overstocked I'd believe him.